Jsp Notes

Tomcat 7

Servlet 3.0
-------------
servelet anno

Synch and Aych processing*

JEE 5 or JEE 6
------------

both are same tech...

MVC

View:jsp

Controller: servlet/ filter

JSP
-----

if both servelt and jsp are same the why two?
-------------------------------------------

CGI and Perl

Servlet

ASP

JSP= Java Server Pages
--------
to simplify the web app development

ASP.net
------

Struts
-------

Velocity
--------

jsp is same as servlet
--------------------------

jsp should be convered in servlet.
------------------------------------

Servlet container

JSP container

JSP is slow then servlet first time only
----------------------------------------
depends on container u are using*

after ward speed of jsp and servlet are same.

What ever we can do in servlet we can do in jsp
----------------------------------------------

Servlet and jsp
==============

how to learn jsp in 1 hr
-------------------------

JSP
===========

Nuts and bolts of JSP
--------------------

diective
-----------
decide behaviour of whole page

<%@ ............ %>

scriptlet
------------

<% %>
pure java code

no html and jsp code

expresssion
------------

<%= i %>

out.prinln(i);

expression is an replacement (Shortcut of out.println() )

decleration
------------

<%! %>

<%! int i=0;%>
<% i++;%>
<%=i%>

to compare jsp with sevlet
----------------------------------

hit counter programs
--------------------

<%!
int i=0;

String fun()
{

ruturn "hi";
}
%>

<%

out.println("i:"+i);
out.print(fun());
%>

<%=i++%>

is equivalent to

<%

out.print(i++);
%>

JSP key topics
=======================
Java bean in jsp

EL

JSTL

JSP std tag liberary

Custome tag

Should be used in place of scriptlet
---------

class MyServlet extends HttpServlet
{
int i=0;

public void fun()
{

out.print("HI");
}

public void doGet(...... req,......res)thr............
{
PrintWriter out=res.get........();

out.println("i:"+i);

out.print("<h1>india is shining?</h1>");
out.print("hi");

fun();
}
}

JSP directive
=============

<%@ .... %>

•page
defines page-specific properties such as character encoding,
the content type for this pages response and whether this

page should have the implicit session object.

<%@ page import="foo.*" session="false" %>

<%@ page language=•java• import=•java.util.Date(),
java.util.Dateformate()•
iserrorpage=•false•%>

A page directive can use up to thirteen different attributes
--------------------

•include
Defines text and code that gets added
into the current page at translation time

<%@ include file="hi.html" %>

•taglib
Defines tag libraries available to the JSP

<%@ taglib tagdir="/WEB-INF/tags/cool" prefix="cool" %>

what is the syn of include directive
--------------------------------

a.jsp
--------------------

<h1>file 1</h2>
<%@ include file="b.jsp" %>

b.jsp
-----------

<h1>file 2</h2>
<h1>india is shining!</h1>
<%=new Date()%>

in theory
---------
we should not use include directive if content of b.jsp

is changing with time.

Scriptlet
=========
<% %>

pure java code
Nothing else only pure java

<% out.println(Counter.getCount()); %>

Expression
=========
<%= %>

<%= Counter.getCount() %>

Instance Declaration
====================
<%! %>

JSP Comments
===========

HTML Comment 

JSP Comment <%-- JSP Comment --%>

Understnading
================

<html>
<body>
<%! int count=0; %>

The page count is now:

<= ++count %>
</body>
</html>

page
for only that page

request doGet(..........request, ........res)

session===>HttpSession s=req.getSession()

application==>getServletContext()

Implicit Object
====================

JspWriter out

HttpServletRequest request

request.setAttribute("key","foo");
String temp=request.getAttribute("key");

HttpServletResponse response

HttpSession session

session.setAttribute("key","foo");
String temp=session.getAttribute("key");

ServletContext application

application.setAttribute("key","foo");
String temp=application.getAttribute("key");

ServletConfig config

Throwable exception

PageContext pageContext (not in servlet)

is an handly way to access any type of scoped variable?

Object page (not in servlet)

Standard Actions
----------------------
Tags that affect runtime behavior of JSP and response send back to client

Std action types:
-----------------
<jsp:useBean>
<jsp:setProperty>
<jsp:getProperty>

RequestDispacher rd=request.getRequestDispacher("show.jsp");
rd.forward(req,res);

<jsp:include>
<jsp:forward>

<jsp:plugin>
<jsp:param>

applet

API for the Generated Servlet
==============================

jspInit()
--------
This method is called from the
init() method and it can be overridden

jspDestroy()
----------
This method is called from the servlets destroy()
method and it too can be overridden

_jspService()

This method is called from the servlets service()
method which means its runs
in a separate thread for each request,
the container passes the request and response
object to this method.

You cannot override this method.

Initializing your JSP
-------------------------

put this in web.xml
---------------------

<web-app ...>

<servlet>
<servlet-name>foo</servlet-name>
<jsp-file>/index.jsp</jsp-file>

<init-param>
<param-name>email</param-name>
<param-value>rgupta.mtech@gmail.com</param-value>
</init-param>

</servlet>

<servlet-mapping>
<servlet-name>foo</servlet-name>
<url-pattern>/index.jsp</url-pattern>
</servlet-mapping>

</web-app>

now getting them in init method
===============================

<%!
public void jspInit()
{

ServletConfig sConfig = getServletConfig();
String emailAddr = sConfig.getInitParameter("email");
ServletContext ctx = getServletContext();
ctx.setAttribute("mail", emailAddr);
}

%>

class Fun
{
Fun(){}

}

now get attributes in service method
===============================

<%= "Mail Attribute is: " + application.getAttribute("mail") %>

<%= "Mail Attribute is: " + pageContext.findAttribute("mail") %>

<%
ServletConfig sConfig = getServletConfig();
String emailAddr = sConfig.getInitParameter("email");
out.println("<br><br>Another way to get web.xml attributes: " + emailAddr );
%>

<%
out.println("<br><br>Yet another way to get web.xml attributes: " +
getServletConfig().getInitParameter("email") );
%>

Setting scoped attributes in JSP
================================

Application
-----------

in servlet
----------
getServletContext().setAttribute("foo",barObj);

in jsp
--------
application.setAttribute("foo",barObj);

Request
--------

in servlet
----------
request.setAttribute("foo",barObj);

in jsp
--------
request.setAttribute("foo",barObj);

Session
--------

in servlet
----------
request.getSession().setAttribute("foo",barObj);

in jsp
--------
session.setAttribute("foo",barObj);

Page
-------

in servlet
----------
do not apply

in jsp
--------
pageContext.setAttribute("foo",barObj);

Note
============

Using the pageContext to get a session-scoped attribute
------------------------------------------------------------

<%= pageContext.getAttribute("foo", PageContext.SESSION_SCOPE ) %>

Using the pageContext to get an application-scoped attribute
----------------------------------------------------------------
<%= pageContext.getAttribute("mail", PageContext.APPLICATION_SCOPE) %>

Using the pageContext to find an attribute
when you don't know the scope
-----------------------------
<%= pageContext.findAttribute("mail") %>

ExceptionHandling in JSP
---------------------------

Exceptionhandling.jsp
--------------------------

<%@ page errorPage="errorpage.jsp" isErrorPage="false"%>
<%

Dog d=null;
String s=null;

....
....
d.toString();

%>

errorpage.jsp
----------------------

<%@ page isErrorPage="true" %>

This is the Error page.The following error occurs:- <br>
<%= exception.toString() %>

Reuqst dispaching vs redirect
------------------------------------

login.html
==========

<form action ="myLogin.jsp".
<input type="text" name="name"/>
<input type="password" name="pass"/>
<input type="submit"/>
</form>

login app
-------------

passing parameter with dispaching
-----------------------------
<jsp:include page="/requestParams2.jsp" >
<jsp:param name="sessionID" value="<%= session.getId() %>" />
</jsp:include>

getting in another servlet and jsp
---------------------------------------

<%@ page import="java.util.*" %>
<%
Enumeration parameterNames = request.getParameterNames();
while (parameterNames.hasMoreElements())
{
String name = (String)parameterNames.nextElement();
out.println(name);
out.println(request.getParameter(name) );
}
%>

Sepration of concern
-------------------
no business logic should be done in jsp at any cost

<jsp:useBean>

<jsp:setProperty>

<jsp:getProperty>

Basic of jsp model
-------------------

script file converted into eq servlet.

no diff between servlet and jsp

nut and bolts of jsp
-----------------

Directive
---------
include

taglib*

attributes not all imp

Scriptlet
-------
pure java code
must be avoided diff to avoide

expression
---------
aka of short cut for out.print()

decleation
----------
<%!

%>

whatever u want to put in insta/static

comments
-------
jsp comm
html comm:show in view source

include directive and include action
----------------------------------------
if content is changing dynamicall always go for action

scope
======
page
request
session
application

pageContext

Std action
---------
<jsp:useBean........./>

<jsp:setProperty ............/>
<jsp:getProperty ............../>

How java bean internally use reflection and serl...?
------------------------------------------------
what is reflection *

============================================================================
Day-2
============================================================================

EL:Expression Language

More on java beans
-------------------

<form action ="LoginServlet" method="get">
ID:<input type="text" name="id"/></br>
Name:<input type="text" name="name"/></br>
Pass:<input type="password" name="pass"/></br>
<input type="submit"/>
</form>

automatic type conversion

processing of bean

Expression Language Introduction ( E L )
-----------------------------------

Putting java code in jsp is bad habbit

then what to do?
---------------

Use EL
JSP 2.0 spec. EL offers a simpler way to
invoke Java code but he code itself belongs somewhere else

Although EL looks like Java it behaves differently,
so do not try and map the same Java with EL.

EL are always within curly braces and prefixed with the dollar sign.

The first named variable in the expression is either an implicit object or
an attribute

how EL make my life easy....
-------------------------------

EL example
------------
old way don't do now
--------------------

Please contact: <%= application.getAttribute("mail") %>

EL way
------

please contact: ${applicationScope.mail}

stop JSP from using scripting elements
--------------------------------------

<web-app ...>
...
<jsp-config>

<jsp-property-group>

<url-pattern>*.jsp</url-pattern>

<scripting-invalid>true</scripting-invalid>

</jsp-property-group>

</jsp-config>
...
</web-app>

stop using EL
-------------
<%@ page isELIgnored="true" %>

Note: this takes priority over the DD tag above

Scriptless JSP
=============

EL provide better way to accept DTO send from controller to view

Some Ex:
======

Consiser Servlet (controller) code
-----------------------------------

Person p = new Person();

p.setName("Paul");

request.setAttribute("person", p);

RequestDispatcher view = request.getRequestDispatcher
("result.jsp");

view.forward(request, response);

JSP (view) code
-----------------
Person is: <%= request.getAttribute("person") %>

Does it work?

Correct way?
--------------
<% Person p = (Person) request.getAttribute("person");

Person is: <%= p.getName() %>

or

Person is: <%= ((Person) request.getAttribute("person")).getName() %>

Correct Way
----------

<jsp:useBean id="person" class="foo.Person" scope="request" />

Person is: <jsp:getProperty name="person" property="name" />

class Person
{

private String name;
....
...
...
}

public class Dog
{
private String dogName;
.....
.....
}

public class Person
{
private String personName;
private Dog dog;

.....
.....
}

Person has A dog
----

Dog dog=new Dog();

dog.setDogName("myDog");

Person p=new Person();

p.setPersonName("foo");

p.setDog(dog);


--------------------------------------------------------------------------------
------

Expression Language
====================

More examples
--------------

consider controller code
----------------------

adding persons dog in request attributes in an servlet
-----------------------------------------------------------

foo.Person p = new foo.Person();

p.setName("Paul");

foo.Dog dog = new foo.Dog();

dog.setName("Spike");

p.setDog(dog);


getting same in jsp
------------------------

using tags

<%= ((Person) request.getAttribute("person")).getDog ().getName() %>

using EL

Dog's name is: ${person.dog.name}

Some more examples
--------------------

in servlet
---------

String[] footballTeams = { "Liverpool", "Manchester Utd", "Arsenal",
"Chelsea" }

request.setAttribute("footballList", footballTeams);

in jsp
---------

Favorite Team: ${footballList[0]}

Worst Team: ${footballList["1"]}

Note ["one"] would not work but ["10"] would

<%-- using the arraylist toString()
---------------------------------

All the teams: ${footballList}

Another Example
--------------

servlet code
----------------

java.util.Map foodMap = new java.util.HashMap();

foodMap.put("Fruit", "Banana");
foodMap.put("TakeAway", "Indian");
foodMap.put("Drink", "Larger");
foodMap.put("Dessert", "IceCream");
foodMap.put("HotDrink", "Coffee");

String[] foodTypes = {"Fruit", "TakeAway", "Drink", "Dessert", "HotDrink"}

request.setAttribute("foodMap", foodMap);

JSP code
---------

Favorite Hot Drink is: ${foodMap.HotDrink}

Favorite Take-Away is: ${foodMap["TakeAway"]}

Favorite Dessert is: ${foodMap[foodTypes[3]]}

EL

JSTL

JSP std tag library
---------------------

core

formatting

sql

xml

String functions

Custom tags
-----------
user defind tags.

in case JSTL dont have tag to solve ur problem.

then go for custom tags

(Dont cook food urself if get cooked food)

Ex:
There may be cases when you want multiple values for one given
parameter name, which is when you use paramValues
============================================================

HTML Form
-----------

<html><body>

<form action="TestBean.jsp">
name: <input type="text" name="name">

ID: <input type="text" name="empID">

First food: <input type="text" name="food">
Second food: <input type="text" name="food">

<input type="submit">
</form>

</body></html>

JSP Code
-----------

Request param name is: ${param.name} <br>

Request param empID is: ${param.empID} <br>

<%-- you will only get the first value -->

Request param food is: ${param.food} <br>

First food is: ${paramValues.food[0]} <br>

Second food is: ${paramValues.food[1]} <br>

Here are some other parameters you can obtain,
-----------------------------------------------------

host header
--------

Host is: <%= request.getHeader("host•) %>

Host is: ${header["host"]}
Host is: $header.host}

whether Request is post or get ?
---------------------------------
Method is: ${pageContext.request.method}

Cookie information
-----------------
Username is: ${cookie.userName.value}

Context init parameter (need to configure in dd)
-----------------------

email is: <%= application.getInitParameter("mainEmail") %>

email is: {$initParam.mainEmail}

What has been covered till now
--------------------------------

directive
--------
<%@ page import="java.util.*" %>

declaration
---------
<%! int y = 3; %>
EL Expression
-------------
email: ${applicationScope.mail}

scriptlet
---------
<% Float one = new Float(42.5); %>

expression
---------
<%= pageContext.getAttribute(foo") %>

action
---------
<jsp:include page="foo.html" />

JSTL
=======

The JSTL is hugh, version 1.2 has five libraries,

four with custom tags and one with a bunch of functions for String manipulation

•JSTL Core - core

•JSTL fmt - formatting

•JSTL XML - xml

•JSTL sql - sql

•JSTL function - string manipulation

Hello world jstl
======================

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html><body>
...
<c:forEach var="i" begin="1" end="10" >
<c:out value="${i}" />
</c:forEach>
...
</body></html>

Custom tags
====================

A Custom tag is a user defined JSP language element.

When a JSP page containing custom tag is translated into a Servlet,

the tag is converted to operations on an object called tag handler.
--------------------

The Web container then invokes those operations when the JSP page•s servlet is
executed.

Note:

1. Custom tags can access all the objects available in JSP pages.

2. Custom tags can modify the response generated by the calling page.

3.Custom tags can be nested.

Custom tag library consists of one or more Java classes

called Tag Handlers and an XML tag library descriptor file (tag library).
---------------- --------------------------

javax.servlet.jsp.tagext.
-----------------------------

A class which has to be a tag handler
needs to implement <<Tag>> or<<IterationTag >> or <<BodyTag>>

or

it can also extend TagSupport or BodyTagSupport class.

Let us create a custom tag which will does substring operation on given input.

If SKIP_BODY
-----------
is returned by doStartTag() then if body is present then it is not
evaluated.

If EVAL_BODY_INCLUDE
-----------------
is returned, the body is evaluated and "passed through" to the current
output.

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